1. Field of the Invention
The invention relates to a scanning device, more particularly to an optical scanning device for scanning an image to be processed by a computer.
2. Description of the Related Art
Referring FIG. 1, a conventional scanning device 1 is used for scanning an image to produce a digital representation which is adapted to be received by a computer. As illustrated, the conventional scanning device 1 includes a case body 3, a transparent scanning panel 5, and a scanning module unit (not visible). The case body 3 includes a broad upper wall 2A and a broad lower wall 2B which is disposed parallel to and which is spaced from the broad upper wall 2A, and has a columnar hollow space which extends downwardly from the broad upper wall 2A to the broad lower wall 2B so as to form an upper annular edge portion that defines an upper annular opening in the upper wall 2A. The transparent scanning panel 5 is fitted to the upper annular edge portion to cover the upper annular opening and defines a scanning area 5A with a size indicating mark on an upper major surface thereof. The scanning module unit is disposed in the case body 3 outboard to the scanning area 5A for producing a scanning line on the image and for transforming the scanned image into a digital representation adapted to be processed by the computer.
In use, the image 2 is placed on the scanning area 5A of the transparent scanning panel 5 after which a cover member 4 is superimposed on the image 2 in order to position the latter in the scanning area SA. The scanning module unit will scan the image 2 and transform the same into the digital representation which is received by the computer. In the event that the image is larger than the size indicating mark and thus exceeds the scanning area 5A, a portion of the image will be left unscanned. The user cannot precisely determine the size of the unscanned portion of the image.